.725 
S972i 
1915 


HE       TERVERTEBRAL 

'  '     IN    MAN 


A.KBERG 


Presented  by 
Robert  C.  Tipton,  D.  0, 


COLLEGE  OF  OSTEOPATHIC  PHYSICIANS 
AND  SURGEONS  •  LOS  ANGELES,  CALIFORNIA 


SWANBERG 


BOOKS 

BY 

HAROLD   SWANBERG 

The  Intervertebral  Foramen 

Octavo  of  101  Pages;   16  Original 
Full-Page    Plates 

Cloth.   $2.0O 


The  Intervertebral  Foramina 
In    Man 

Crown  8  vo.  of  95   Pages;    11   Original 
Full-Page  Plates 

Cloth,  $1.75 


CHICAGO   SCIENTIFIC   PUBLISHING   Co. 


THE  JNTER VERTEBRAL 
FORAMINA  IN  MAN? 

THE  MORPHOLOGY  OF  THE  INTERVERTEBRAL  FORAMINA  IN  MAN 
INCLUDING  A  DESCRIPTION  OF  THEIR  CONTENTS  AND  ADJACENT 
PARTS  WITH  SPECIAL  REFERENCE  TO  THE  NERVOUS  STRUCTURES 

(Supplement  to  "The  Intervertebral  Foramen") 

BY 

HAROLD    SWANBERG 

Member  American  Association  for  the  Advancement  of  Science 


With  an  Introductory  Note 

BY 
PROF.   HARRIS   E.  SANTEE 


From  the  Anatomical  Laboratory,  Chicago  College 
of  Medicine  and  Surgery 

Illustrated  by  11  original  full -page  plates 


CHICAGO  SCIENTIFIC  PUBLISHING  CO. 

221   South  Ashland  Boulevard 

CHICAGO,   ILLINOIS 

1915 


COPYRIGHT,  1915 

BY 
HAROLD    SWAN BERG 


All  Rights  Reserved 


To  MY  SISTER 
/iDarton  (Boers  Swanbero 

THIS   BOOK    IS 
AFFECTIONATELY  DEDICATED 


INTRODUCTORY  NOTE 


BY 


HARRIS   E.   SANTEE,   A.  M.,  M.  D.,   Ph.  D. 


|R.  HAROLD  SWAN  BERG  has  enlarged  the  scope 
of  his  contribution  to  anatomic  knowledge  by  pur- 
°*ga^l  suing  his  investigation  to  its  logical  conclusion. 
His  former  work,  to  which  I  wrote  a  prefatory  note,  was 
done  upon  the  intervertebral  foramina  of  lower  animals. 
That  work  is  fully  corroborated  and  greatly  enhanced  by 
the  present  monograph,  which  presents  an  equally  careful 
study  of  the  human  intervertebral  foramina.  In  the  light 
of  this  new  knowledge,  certain  theories  of  spinal  tension 
and  compression  must  be  greatly  modified.  The  undoubted 
anatomic  facts,  revealed  by  Mr.  Swanberg  in  this  pains- 
taking, scientific  work,  .necessitate  a  complete  restatement 
of  the  rationale  of  "cures"  effected  by  spinal  manipulation. 


PREFACE 

|  HE  very  favorable  reception  which  has  been  ac- 
corded my  book,  "The  Intervertebral  Foramen," 
has  stimulated  me  to  further  study  on  this  subject. 
In  the  above  work  are  found  a  histologic  description  and 
photomicrographs  of  an  intervertebral  foramen,  its  con- 
tents and  adjacent  parts — the  first  to  appear  in  the  liter- 
ature. The  foramen  described  was  taken  from  a  cat. 
Since  the  publication  of  the  above  I  have  been  in  receipt 
of  many  inquiries  as  to  whether  the  description  given 
could  be  relied  upon  to  be  identical  with  that  in  man. 
From  the  information  gained  by  numerous  dissections  of 
intervertebral  foramina  in  man  the  description  given  of 
the  foramen  in  the  cat  would  appear  to  be  similar  to  that 
in  man.  However,  in  order  to  scientifically  settle  this 
question  I  made  a  microscopic  study  of  several  interver- 
tebral foramina  and  their  adjacent  parts  in  man.  These 
findings  corroborate  those  described  in  the  original  work. 
While  no  two  intervertebral  foramina  were  found  to  be 
identical  they  all  have  a  similar  structure.  The  above 
findings  were  briefly  reported  in  the  JOURNAL  OF  THE  AMERI- 
CAN MEDICAL  ASSOCIATION,  Oct.  31,  1914,  and  the  MEDICAL 
RECORD,  Nov.  14,  1914,  and  later  followed  by  an  article 
entitled,  "The  Intervertebral  Foramina  in  Man"  in  the 
MEDICAL  RECORD,  Jan.  30,  1915. 

11 


12  PREFACE 

In  the  present  text  I  have  endeavored  to  give  a  de- 
tailed description  of  the  normal  morphology  of  the  inter- 
vertebral  foramina  in  man,  including  their  contents  and 
immediately  adjacent  parts.  The  importance  of  an  intri- 
cate knowledge  of  the  morphology  of  these  apertures 
hardly  need  be  emphasized.  During  the  past  quarter 
of  a  century  a  great  deal  of  attention  has  been  directed  to  the 
vertebral  column  from  a  therapeutical  standpoint.  Many 
schools  have  arisen  claiming  that  the  great  majority  of 
diseases  have  their  origin  from  various  spinal  abnormalities 
which  produce  pathologic  changes  in  the  intervertebral 
foramina,  their  contents,  or  surrounding  tissues.  It  is  not 
the  purpose  of  this  book  to  argue  the  case  one  way  or  the 
other  but  to  present,  as  above  mentioned,  a  clear  and  concise 
description  of  the  normal  morphology  of  these  apertures  and 
parts  in  man.  Once  the  normal  structure  is  thoroughly  mas- 
tered, the  reader  will  then  be  in  a  better  position  to  judge  for 
himself  the  effects  of  pathologic  changes  ;  he  can  then  formu- 
late his  own  opinion  concerning  the  theories  of  nerve  pres- 
sure, irritation,  or  other  pathologic  phenomena  occurring  in 
the  intervertebral  foramina  or  adjacent  tissues,  as  a  causative 
factor  in  disease. 

The  Anglicized  form  of  the  Basle  anatomical  termi- 
nology (BNA)  is  used  throughout.  To  facilitate  a  quick 
reading  of  the  work  the  less  important  details  are  printed 
in  small  type. 

Although  the  work,  in  general,  is  entirely  original  I  am 
indebted  to  the  anatomies  of  Morris,  Gray,  Cunningham, 
and  Santee  for  references. 


PREFACE  13 

Zan  D.  Klopper,  M.  D.,  of  Chicago,  has  drawn  plates 
1,  2,  3  and  5  and  did  the  retouching  of  the  photomicro- 
graphs. I  have  sketched  plates  4  and  6. 

I  desire  to  express  my  sincere  thanks  to  my  friend 
and  preceptor  in  anatomy,  Harris  E.  Santee,  A.  M., 
Ph.  D.,  M.  D.,  Professor  of  Neural  Anatomy,  Chicago  Col- 
lege of  Medicine  and  Surgery,  for  reviewing  the  work ;  to 
William  L.  Copeland,  M.  R.  C.  S.,  C.  M.,  M.  D.,  Professor 
and  Head  of  the  Department  of  Anatomy,  Chicago  College 
of  Medicine  and  Surgery,  for  his  kindness  in  supplying  ma- 
terial for  dissection ;  to  Wayne  W.  Bissell,  B.  S.,  M.  D., 
Resident  Pathologist,  Cook  County  Hospital,  Chicago,  for 
permission  to  secure  several  specimens  from  autopsies ; 
to  Mr.  Herbert  D.  Ulmer  for  assistance  in  dissecting; 
and  especially  to  Mrs.  Sarah  Jordan  Kerns  for  her  in- 
valuable aid  in  correcting  the  original  manuscript. 

CHICAGO,  May,  1915. 

HAROLD  SWANBERG. 


PUBLISHERS'    INTRODUCTION 

The  extremely  favorable  reception  which  Swanberg's  mono- 
graph "The  Intervertebral  Foramen"  has  received,  has  been  most 
gratifying.  That  work,  which  fills  a  certain  hiatus  in  the 
anatomical  literature,  has  been  greatly  enhanced  by  the  present 
supplement,  which  presents  for  the  first  time  an  exhaustive  de- 
scription of  the  morphology  of  the  human  intervertebral 
foramina,  including  their  contents  and  adjacent  parts. 

A  few  reviews  of  the  original  work  are  appended: 

Medical  Review  of  Reviews. 

"Swanberg,  in  a  very  original  and  careful  volume,  estab- 
lishes the  histology  of  the  areas  forming  the  intervertebral  fora- 
men. Scientifically  accurate,  it  forms  a  basic  monograph  upon 
the  subject  it  discusses.  Original  plates,  careful  explanations, 
thoroughness  in  details,  and  with  a  most  admirable  conciseness 
add  to  the  value  of  an  anatomic  study  which  will  be  helpful  to 
those  interested  in  the  anatomy  and  histology  of  the  spinal 
column.  .  .  .  .  The  science  of  anatomy  is  replete  with  simi- 
lar topics  worthy  of  investigation,  and  the  profession  will  be  for- 
tunate if  they  are  equally  ably  investigated  and  reported  as  has 
been  the  intervertebral  foramen." 

American  Journal  of  the  Medical  Sciences. 
"The  investigations  of  Swanberg  emphasize  the  fact  that 
slight  changes  in  relationship  in  the  spinal  structures  may  give 
rise  to  varied  symptoms.  The  work  here  presented  is  highly 
commendable  and  bears  evidence  of  a  thorough  and  careful  in- 
vestigation. To  persons  interested  in  nervous  diseases  and  also 
in  mechanical  disturbances  of  the  spine,  this  book  should  be  of 
usual  interest  and  value." 

Canada  Lancet. 
"This   book  is  absolutely  unique.     It  is  the  first  and   only 

scientific  work  on  this  subject This  work  contains  no 

theories.  One  can  see  these  parts  just  as  they  normally  are.  You 
can  then  formulate  your  own  opinion  about  nerve  pressure,  im- 
pingement, irritation,  etc.,  as  a  cause  of  disease.  It  is  a  book 
every  progressive  physician  should  have.  To  the  careful  perusal 
of  anatomists  everywhere,  we  have  pleasure  in  introducing  this 
work." 

New  York  Medical  Journal. 

"It  has  taken  the  author  four  years  to  complete  his  re- 
searches, and  they  are  therefore  of  great  scientific  interest  as  well 

as  possible  therapeutic  value The  book  is  of  value  to 

those  interested  in  the  therapeutics  of  the  spine,  and  the  author 
deserves  great  credit  for  his  patient  investigations  in  this  inter- 
esting field." 

14 


TABLE   OF  CONTENTS 

PAGE 

Introduction    .  19 


PART    I 

GENERAL  DESCRIPTION   OF  THE 
INTERVERTEBRAL    FORAMINA 

I.     Introduction     23 

II.     Boundaries  of  the  Intervertebral  Foramina 25 

III.  Shape  and  Relative  Size  of  the  Intervertebral  Foramina  35 

IV.  Modified    Intervertebral    Foramina 41 

V.     Constituents   of  the  Intervertebral  and   Modified   Inter- 
vertebral  Foramina   43 

1 .  Spinal    Nerves    43 

(a)  Anatomy    43 

(b)  Relative  Size    44 

(c)  Location  and  Divisions  in  the  Intervertebral 

Foramina     45 

2.  Arteries     47 

3.  Veins   49 

4.  Fat    Tissue    51 

5.  Fibrous    Tissue    52 

6.  Lymphatics    '. 52 

VI.     Sizes  of  the  Intervertebral  Foramina  as  Compared  to  the 

Spinal    Nerves    54 

15 


16  TABLE  OF  CONTENTS 

PART    II 

DETAILED   DESCRIPTION   OF  AN   INTERVERTEBRAL 
FORAMEN  AND  ITS  ADJACENT  PARTS 

PAGE 

Introduction    59 

Description  of  Plate    5    62 

Description  of  Plate     *>    66 

Description  of  Plate     7    (Section  38)    70 

Description  of  Plate    8    (Section  30)    74 

Description  of  Plate    9   (Section  27)    78 

Description  of  Plate  10    (Section  23)    82 

Description  of  Plate  11   (Special)    86 

Summary   of  this    Intervertebral   Foramen    and   its   Adjacent 

Parts             89 


PART    III 

SUMMARY 
General   Summary    93 


LIST   OF   PLATES 

PLATE  PAGE 

1.  Two  adjacent  typical  cervical  vertebrae  with  the  interver- 

tebral  fibre-cartilage  connecting  them 27 

2.  Two    adjacent    typical   thoracic   vertebrae   with    the   inter- 

vertebral    fibro-cartilage   connecting   them   and   the    head 
and  neck  of  a  typical  rib 29 

3.  Two  adjacent  typical  lumbar  vertebrae  with  the  interverte- 

bral   fibro-cartilage  connecting  them 31 

4.  The  size  and  shape  of  a  cervical,  thoracic  and  lumbar  in- 

tervertebral    foramen   and  the   position   and   size   of   the 
spinal  nerves  they  convey  (outline  drawing) 37 

5.  Seventh  and  eighth  thoracic  vertebrae  with  the  interverte- 

bral    fibro-cartilage   connecting   them   and   the   head   and 
neck  of  the  right  eighth  rib 63 

6.  Right  seventh  thoracic  intervertebral  foramen  and  its  adja- 

cent bony  boundaries   (outline  drawing) 67 

7.  Right  seventh  thoracic  intervertebral  foramen  and  its  adja- 

cent bony  boundaries 71 

8.  Immediately  lateral  to  the  right  seventh  thoracic  interverte- 

bral foramen  75 

9.  Lateral  to  the  right  seventh  thoracic  intervertebral  foramen 

lateral  to  Plate  8 79 

10.  Lateral  to  the  right  seventh  thoracic  intervertebral  foramen 

lateral  to  Plate  9 83 

11.  Lateral  to  the  right  first  thoracic  intervertebral  foramen  ...     87 


17 


INTRODUCTION 

HE  purpose  of  this  book  is  to  present  an  accurate 
and  scientific  description  of  the  normal  morphology 
of  the  intervertebral  foramina  in  man,  including  a 
complete  description  of  the  contents  of  the  foramina  and 
their  immediately  adjacent  parts,  with  special  reference  to 
the  nervous  structures. 

For  convenience,  the  text  which  follows  is  divided  into 
three  parts: 

1.  A  general  description  of  the  intervertebral  foramina 
and  their  contents. 

2.  A  detailed  description  of  one  particular  interverte- 
bral   foramen    and    its    immediately    adjacent    parts,    with 
photomicrographs. 

3.  A    summary   based   upon   careful    examinations   of 
numerous   intervertebral   foramina,  and  their   surrounding 
tissues. 

This  will  give  one  an  excellent  idea  as  to  the  general 
structure  of  all  the  intervertebral  foramina. 


19 


PART   I 


GENERAL    DESCRIPTION    OF   THE 
INTERVERTEBRAL    FORAMINA 


I.    INTRODUCTION 


HE  intervertebral  foramina  are  apertures  formed  by 
the  articulation  of  two  contiguous  vertebrae.  They 
serve  to  transmit  spinal  nerves,  arteries,  veins,  and 
in  all  probability  lymphatics. 

There  are  twenty-three  pairs  of  intervertebral  fora- 
mina extending  without  interruption  from  the  epistropheus 
(axis)  to  the  sacrum.  Although  no  two  are  identical,  all 
have  a  similar  structure.  The  first  pair  is  situated  between 
the  epistropheus  and  third  cervical  vertebra  and  the  last  be- 
tween the  fifth  lumbar  vertebra  and  the  sacrum.  Spaces  or 
apertures  that  are  not  spoken  of  as  intervertebral  foramina 
are  found  however,  between  the  occipital  bone  and  atlas,  the 
atlas  and  epistropheus,  the  rudimentary  sacral  vertebrae, 
and  the  sacrum  and  coccyx,  which  transmit  spinal  nerves 
and  vessels.  They  may  be  considered  as  modified  interverte- 
bral foramina  and  will  be  discussed  later. 

The  intervertebral  foramina,  like  the  spinal  nerves  and 
vertebrae,  are  named  according  to  the  region  of  the  vertebral 
column  in  which  they  are  located,  i.  e.,  cervical,  thoracic, 
and  lumbar.  The  following  table  shows  their  number  in 

23 


THE  INTERVERTEBRAL  FORAMINA  IN  MAN 


each  region  of  the  column  as  compared  with  the  number 
of  spinal  nerves  and  vertebrae : 


Region 

Intervertebral 
Foramina 

Nerves 

Vertebrae 

Cervical    

6  pairs 

8  pairs 

7 

Thoracic    

12     " 

12     " 

12 

Lumbar    

5     " 

5     " 

5 

Sacral    

5     " 

5 

Coccygeal   

1  pair 

4 

23  pairs 

31  pairs 

33 

II.     BOUNDARIES   OF  THE   INTERVERTEBRAL 
FORAMINA 

The  boundaries  of  the  intervertebral  foramina  have  a 
similar  arrangement  throughout.  Each  intervertebral  fora- 
men is  almost  entirely  surrounded  by  bone,  the  intervertebral 
fibre-cartilages  completing  the  boundary.  The  bony  bound- 
aries are  parts  of  two  adjacent  vertebrae,  though  in  the 
thoracic  region  the  heads  of  the  ribs,  from  the  second  to  the 
ninth,  inclusive,  also  assist  in  forming  the  boundaries  for 
the  first  eight  thoracic  pairs. 

The  boundaries  of  the  intervertebral  foramina  are  as 
follows:  (Plates  1,  2,  3.) 

Anterior. 

C  Body  of  upper  vertebra. 
Cervical,  Lumbar,  and      I  T 

-,.,,_,  •<  Intervertebral   fibro-cartilage. 

Twelfth  Thoracic  ,  , 

v^Body  of  lower  vertebra. 

f  Body  of  upper  vertebra. 
Upper  Eight  Thoracic  X  Head  of  rib. 

(^  Intervertebral  fibro-cartilage. 

Ninth,  Tenth  and  f  Body  of  upper  vertebra. 

Eleventh  Thoracic  (  Intervertebral  fibro-cartilage. 

In  the  cervical  and  lumbar  regions,  the  roots  of  the  vertebral 
arches  (pedicles)  do  not  take  origin  from  the  extreme  upper  part 
of  the  bodies  of  the  vertebrae.  Hence  the  superior  and  inferior 

25 


26  THE  INTERVERTEBRAL  FORAMINA  IN  MAN 

vertebral  notches  are  large,  though  the  superior  is  smaller,  especially 
in  the  lumbar  region.  Therefore  the  cervical  and  lumbar  inter- 
vertebral  foramina  have  parts  of  both  adjacent  vertebral  bodies 
assisting  in  forming  their  anterior  boundary. 

In  the  thoracic  region  the  roots  (pedicles)  take  origin  from 
the  extreme  upper  part  of  the  bodies  of  the  vertebrae.  Hence  the 
inferior  vertebral  notches  are  very  large  and  the  superior  vertebral 
notches  are  only  faintly  marked.  Therefore  these  intervertebral 
foramina,  with  the  exception  of  the  twelfth  pair,  have  but  a  part 
of  one  vertebral  body  assisting  in  forming  their  anterior  boundary. 
The  twelfth  thoracic  pair  is  bounded  anteriorly  by  both  the  bodies 
of  the  twelfth  thoracic  and  the  first  lumbar  vertebrae  because  of 
the  root  of  the  first  lumbar  not  taking  origin  from  the  extreme 
upper  part  of  the  body. 


Posterior. 

Through-  (  Inferior  articular  process  of  upper  vertebra, 
out          )  Superior  articular  process  of  lower  vertebra. 


The  articular  processes  are  held  together  by  a  capsular  liga- 
ment which  forms  the  immediate  posterior  boundary  of  the  inter- 
vertebral  foramina.  These  capsular  ligaments,  which  are  composed 
partly  of  white  fibrous  tissue  and  partly  of  yellow  elastic  tissue, 
are  most  lax  in  the  cervical  and  most  tense  in  the  thoracic  region. 

Superior. 

Cervical,  / 

Thoracic,  and    J  Root  (pedicle)  of  upper  vertebra. 

Upper  Lumbar  ( 

(  Root  of  upper  vertebra. 
Lower  Lumbar   < 

(   1  ransverse  process  of  upper  vertebra. 


PLATE  1 


A  right  lateral  view  of  two  adjacent  typical  cervical  vertebrae 
with  the  intervertebral  fibro-cartilage  connecting  them.  It  shows 
a  cervical  intervertebral  foramen  and  its  adjacent  boundaries.  Life 
size.  (The  vertebrae  are  the  fourth  and  fifth  cervical.) 


A — Inferior      articular      process     of 

upper  vertebra. 

B — Root  (pedicle)  of  upper  vertebra. 
C — Body  of  upper  vertebra. 
D — Intervertebral    fibro-cartilage. 


K — Body  of  lower  vertebra. 
F — Root  (pedicle)  of  lower  vertebra. 
C — Superior     articular     process     of 
lower   vertebra. 


PLATE  2 


29 


A  right  lateral  view  of  two  adjacent  typical  thoracic  vertebrae 
with  the  intervertebral  fibro-cartilage  connecting  them,  and  the 
head  of  a  typical  rib  articulating  with  these  vertebrae  and  inter- 
vertebral  fibro-cartilage.  It  shows  a  thoracic  intervertebral  fora- 
men and  its  adjacent  boundaries.  Life  size.  (The  vertebrae  are 
the  seventh  and  eighth  thoracic,  and  the  rib  the  head  of  the  right 
eighth.) 


A — Inferior      articular      process      of 

upper   vertebra. 

P. — Root  (pedicle)  of  upper  vertebra. 
C — Body  of  upper  vertebra. 
D — Intervertebral    fibro-cartilage. 


1C — Head  of  rib. 

F — Root  (pedicle)  of  lower  vertebra. 
C — Superior     articular     process     of 
lower  vertebra. 


PLATE  3 


31 


A  right  lateral  view  of  two  adjacent  typical  cervical  vertebrae 
with  the  intervertebral  fibro-cartilage  connecting  them.  It  shows 
a  lumbar  intervertebral  foramen  and  its  adjacent  boundaries.  Life 
size.  (The  vertebrae  are  the  third  and  fourth  lumbar.) 


A — Inferior     articular     process      of 

upper   vertebra. 

T! — Root  (pedicle)  of  upper  vertebra. 
C — Body   of   upper   vertebra. 
D — Intervertebral    fibro-cartilage. 


K — Body  of  lower  vertebra. 
F — Root  (pedicle)  of  lower  vertebra. 
G — Superior     articular     process     of 
lower  vertebra. 


BOUNDARIES  OF  INTERVERTEBRAL  FORAMINA  33 

Inferior. 

Cervical,  C 

Thoracic,  and     J  Root  (pedicle)  of  lower  vertebra. 

Upper  Lumbar   (^ 

(  Root  of  lower  vertebra. 
Lower  Lumbar  |  Transverse  process  of  lower  vertebra. 

In  the  upper  part  of  the  lumbar  region  the  transverse  processes 
arise  from  the  junction  of  the  laminae  and  roots  (pedicles),  but 
descending  they  advance  taking  their  origin  from  the  lateral  sur- 
face of  the  roots  and  finally  from  the  sides  of  the  bodies  as  well. 
This  arrangement  explains  why  the  superior  and  inferior  boundaries 
of  the  lower  lumbar  intervertebral  foramina  are  partly  formed  by 
the  transverse  processes. 

The  boundaries  of  the  intervertebral  foramina  are  smooth. 
They  are  covered  by  periosteum,  capsular  ligaments  connecting  the 
articular  processes,  the  posterior  longitudinal  (posterior  common) 
and  lateral  vertebral  ligaments  covering  the  vertebral  bodies,  and 
the  intervertebral  fibro-cartilages. 

The  anterior  and  posterior  boundaries  of  the  intervertebral 
foramina  in  the  thoracic  and  lumbar  regions  are  in  the  same  sagittal 
plane  on  account  of  the  articular  processes  and  bodies  of  the 
vertebrae  projecting  equi-laterally.  The  superior  and  inferior 
boundaries  are  also  in  the  same  sagittal  plane  on  accourt  of  the 
roots  (pedicles)  projecting  directly  posteriorly  from  the  lateral 
extremities  of  the  bodies.  In  the  cervical  region  the  roots  project 
laterally  as  well  as  posteriorly,  with  the  result  that  the  articular 
processes  are  more  laterally  situated  than  are  the  bodies,  and  the 
various  boundaries  are  not  in  the  same  sagittal  plane.  Therefore 
the  intervertebral  foramina  are  all  directed  laterally  except  in  the 
cervical  region.  Here  they  are  directed  antero-laterally. 

Due  to  the  peculiar  arrangement  of  the  transverse  and  articular 
processes  in  the  cervical  region,  the  bony  relations  lateral  to  the 
intervertebral  foramina  form  directly  continuous,  incomplete,  osseous 


34          THE  INTERVERTEBRAL  FORAMINA  IN  MAN 

canals,  through  which  pass  the  spinal  nerves  and  vessels.  Like  the 
cervical  intervertebral  foramina  they  are  directed  antero-laterally. 
In  the  lumbar  region  the  bony  boundaries  of  the  intervertebral 
foramina  are  so  massive  that  they  might  be  considered  as  osseous 
canals.  This  is  especially  true  in  the  lower  lumbar  region  where 
the  transverse  processes  assist  in  forming  the  superior  and  inferior 
boundaries. 


III.     SHAPE  AND  RELATIVE  SIZE  OF  THE 
INTERVERTEBRAL    FORAMINA 

Shape.  The  shapes  of  the  intervertebral  foramina  in  the 
several  regions  are  distinctive  from  one  another,  but  all  in 
each  region  are  similar.  However  they  are  all  more  or  less 
oval  with  the  greatest  diameter  in  a  supero-inferior  direction. 
The  largest  antero-posterior  diameter  of  the  cervical  in- 
tervertebral foramina  is  through  the  middle ;  of  the  thoracic 
and  lumbar,  through  the  upper  part.  Their  respective  shapes 
can  be  best  understood  by  a  study  of  Plate  4. 

Relative  Size.  On  account  of  their  shapes  it  is  very 
difficult  to  estimate  accurately  the  comparative  sizes  of  the 
intervertebral  foramina.  However  the  cervical  and  upper 
thoracic  foramina  are  approximately  of  equal  size  and  are 
about  10  mm.  (^  in.)  in  their  greatest  diameter.  Beginning 
with  the  middle  thoracic  region  they  gradually  increase  in 
size  from  above  downward  to  the  fourth  lumbar,  the 
largest  foramina  being  those  of  the  middle  lumbar  region, 
which  are  about  18  mm.  (^  in.)  in  their  greatest  diameter. 
The  fifth  lumbar  intervertebral  foramina  are  not  the  largest 
pair  as  is  commonly  thought,  as  the  comparative  thinness  of 
the  posterior  part  of  the  fifth  lumbar  vertebral  body  and 
corresponding  intervertebral  fibro-cartilage  greatly  reduces 
their  supero-inferior  diameter.  The  intervertebral  foramina 
are  subject  to  changes  in  size  and  shape,  depending  upon 
the  position  of  the  vertebral  column.  Their  size  is  de- 

35 


36 


THE  INTERVERTEBRAL  FORAMINA  IN  MAN 


pendent  to  a  very  great  extent  upon  the  condition  of  the  liga- 
ments and  muscles  connecting  the  vertebrae;  particularly 
upon  the  thickness  of  the  intervertebral  fibre-cartilages 
and  the  articular  cartilage  on  the  articular  processes,  espe- 
cially the  former. 

In  order  that  the  reader  may  have  a  better  understanding  of 
the  size  of  the  intervertebral  foramina,  the  following  measurements 
of  the  supero-inferior  diameter  (greatest  diameter),  which  were 
taken  from  the  vertebral  column  of  a  male  adult,  are  given.  This 
column  was  of  normal  length,  75  cm.  (30  in.),  and  devoid  of  any 
pathologic  curvatures. 


Intervertebral 
Foramen 

Supero-inferior 
Diameter 

Intervertebral 
Foramen 

Supero-inferior 
Diameter 

3  C. 

10.5  mm. 

7  T. 

13.5  mm. 

4 

8.5 

8 

14. 

5 

9.5 

9 

14. 

6 

10. 

10 

14. 

7 

10. 

11 

15. 

8 

10. 

12 

16. 

1 

'. 

10. 

1 

L 

18. 

2 

10. 

2 

19. 

3 

10. 

3 

18. 

4 

11. 

4 

17.5 

5 

13. 

5 

12. 

6 

13. 

Intervertebral  Fibro-Cartilages.  The  intervertebral  fibre-car- 
tilages are  twenty-three  in  number.  They  are  compressible  discs 
of  white  fibrous  tissue  and  fibrous  cartilage,  tough  but  elastic, 
which  are  interposed  between  the  bodies  of  the  vertebrae  from 
the  epistrophciis  (axis)  to  the  sacrum  and  assist  in  forming  the 
anterior  boundaries  of  all  the  intervertebral  foramina.  Similar 
fibro-cartilages  are  found  between  the  segments  of  the  sacrum  and 
coccyx  in  the  younger  stages  of  life,  but  they  undergo  ossification 


PLATE  4 


37 


Cervical 


Thoracic 


Lumbar 


The  size  and  shape  of  a  cervical,  thoracic  and  lumbar  inter- 
vertebral  foramen  and  the  position  and  size  of  the  spinal  nerves 
they  convey.  The  intervertebral  foramina  shown  are  the  sixth 
cervical,  seventh  thoracic  and  second  lumbar.  (2  diameters.) 
Outline  drawing. 


SHAPE  AND  SIZE  OF  INTERVERTEBRAL  FORAMINA     39 

at  their  surface  and  often  throughout  their  whole  extent  soon  after 
puberty.  The  intervertebral  fibro-cartilages  form  the  chief  bond 
of  union  between  the  vertebrae,  corresponding  in  shape  with  the 
bodies  of  the  vertebrae  they  unite.  The  elasticity  of  the  vertebral 
column  is  dependent  to  a  considerable  extent  upon  them.  They 
tend  to  restore  the  column  to  its  natural  curvature  after  it  has 
been  deflected  by  muscular  action. 

In  thickness  the  intervertehral  fibro-cartilages  vary  not  only 
in  the  different  regions  of  the  vertebral  column  but  in  different 
parts  of  the  same  disc.  This  variation  in  different  parts  of  the 
same  fibre-cartilage  contributes  much  to  the  formation  of  the 
natural  curvatures  of  the  vertebral  column.  In  the  cervical  and 
lumbar  regions  they  are  thicker  in  front  than  behind,  thereby  pro- 
ducing the  anterior  convexity  of  the  cervical  region,  and  increas- 
ing that  of  the  lumbar  region.  In  the  thoracic  region  they  are 
slightly  thinner  in  front  than  behind,  thereby  increasing  to  a  small 
extent  the  anterior  concavity  of  this  region. 

Measuring  along  their  anterior  surface  the  intervertebral  fibro- 
cartilages  average  between  4  and  5  mm.  (]/$  in.)  in  the  cervical 
and  thoracic  regions  and  about  13  to  14  mm.  (A  in.)  in  the  lumbar 
region.  The  thinnest  intervertebral  fibro-cartilages  are  from  the 
third  to  the  seventh  thoracic  vertebrae,  measuring  from  2  to  3  mm. 
(rV  in.)  ;  the  thickest  is  between  the  fifth  lumbar  and  sacrum,  and 
is  much  thicker  in  front  than  behind,  being  about  18  mm.  (^  in.) 
on  its  anterior  surface  and  about  one-half  this  thickness  on  its 
posterior  surface.  The  latter  fibro-cartilage,  due  to  its  wedge-like 
shape,  greatly  aids  in  the  formation  of  the  prominent  angle  situated 
at  the  lumbo-sacral  junction  called  the  promontory  (sacro-vertebral 
angle).  The  intervertebral  fibro-cartilages  form  nearly  one-quarter 
of  the  entire  length  of  the  vertebral  column. 

In  order  that  the  reader  may  have  a  better  understanding  of 
the  thickness  of  the  intervertebral  fibro-cartilages,  the  following 
measurements,  which  were  taken  from  the  vertebral  column  above 
mentioned,  are  given.  The  thickness  of  each  intervertebral  fibro- 
cartilage  was  measured  in  the  median  plane  on  (1)  its  anterior 
surface,  (2)  its  median  cut  surface  and  (3)  on  its  posterior  surface. 


40 


THE  INTERVERTEBRAL  FORAMINA  IN  MAN 


Intervertebral 
Fibro-Cartilage 

Anterior 
Surface 

Median 
Cut  Surface 

Posterior 
Surface. 

3  C. 

4.5  mm. 

5.     mm. 

4.    mm. 

4   " 

5.      " 

5.      " 

2.5    " 

5    ' 

5.5    " 

5.5    " 

3.      " 

6    ' 

5.      " 

4.5    " 

2.      " 

7 

3.5    " 

4.5    " 

2.5    " 

8 

3.5    " 

5.5    " 

3.      " 

1  T. 

3.      " 

5.5    " 

3.5    " 

2 

2.5    " 

5.5    " 

3.      " 

3 

2.      " 

6.      " 

3.5    " 

4 

2       " 

5.       ' 

2.      " 

5 

<>'      " 

4.5     ' 

2.5    " 

6 

2.5    " 

4.       ' 

2.5    " 

7 

3.       ' 

3.       ' 

2.      " 

8 

4.5     ' 

4.       ' 

2.      " 

9 

4.5     ' 

5.       ' 

2.5    " 

10 

7.       ' 

5.       ' 

3.5    " 

11 

8.       ' 

5.5     ' 

4.      " 

12 

10.      " 

6.       ' 

4.5    " 

1  L. 

11.      " 

9.5     ' 

7.      " 

2 

12.      " 

12.       ' 

7.5    " 

3 

14.      " 

14.       ' 

8.      " 

4 

17.5    " 

15.       ' 

10.      " 

5 

19.      " 

13.5     ' 

7.5    " 

Articular  Cartilages.  An  articular  cartilage  is  found  on  each 
articular  process  of  all  the  vertebrae.  It  is  composed  of  hyaline 
cartilage  and  corresponds  in  size  and  shape  with  the  articular  part 
of  the  process  upon  which  it  is  situated.  It  covers  the  entire  ar^a 
of  that  part  of  the  articular  process  which  articulates  with  its 
fellow.  Each  cartilage  is  less  than  1  mm.  (1/25  in.)  in  thickness 
and  adheres  very  closely  to  the  bone. 


IV.     MODIFIED  INTERVERTEBRAL  FORAMINA 

There  are  seven  pairs  of  what  may  be  called  modified 
intervertebral  foramina;  two  in  the  cervical,  and  five  in  the 
sacral  region.  The  only  point  in  which  they  all  differ  from 
the  intervertebral  foramina  is  that  there  is  no  intervertebral 
fibre-cartilage  in  connection  with  them. 

The  two  pairs  of  modified  cervical  intervertebral  fora- 
mina are  situated  between  the  occipital  bone  and  the  poster- 
ior arch  of  the  atlas,  and  the  posterior  arch  of  the  atlas  and 
the  laminae  of  the  epistropheus  (axis),  respectively.  They 
are  very  incompletely  surrounded  by  bone,  are  directed  in 
a  lateral  manner,  and  are  converted  into  more  or  less  definite 
spaces  by  the  assistance  of  the  soft  tissues.  These  spaces 
are  subject  to  changes  in  size  and  shape  with  movements  of 
this  portion  of  the  vertebral  column. 

Of  the  five  pairs  of  modified  intervertebral  foramina  in 
the  sacral  region,  the  upper  four  are  situated  between  the 
rudimentary  sacral  vertebrae.  They  are  completely  sur- 
rounded by  bone  and  being  permanent  in  size  and  shape,  are 
not  influenced  by  changes  in  position  of  this  region  of  the 
vertebral  column.  Due  to  the  fusion  of  all  the  sacral  verte- 
brae to  form  a  single  bone,  osseous  canals  are  formed  with 
which  these  foramina  are  continuous ;  the  openings  of  which 
on  the  anterior  surface  of  the  sacrum  are  called  the  anterior 
sacral  foramina,  and  on  the  posterior  surface,  the  posterior 
sacral  foramina.  The  posterior  foramina  are  less  regular  in 

41 


42  THE  INTERVERTEBRAL  FORAMINA  IN  MAN 

form,  much  smaller  in  size  and  their  margins  much  sharper 
than  the  corresponding  anterior  foramina.  The  last  pair  of 
sacral  modified  intervertebral  foramina  is  situated  between 
the  sacrum  and  coccyx.  Between  these  bones  a  thin  fibro- 
cartilaginous  disc  is  interposed.  These  foramina  are  not  en- 
tirely surrounded  by  bone,  the  fibro-cartilaginous  disc  and 
soft  tissues  completing  the  boundary,  therefore  they  are  sub- 
ject to  changes  in  size  and  shape,  with  the  vertebral  move- 
ments of  this  region.  They  are  also,  as  are  the  first  four 
sacral  pairs,  divided  anteriorly  and  posteriorly.  The  sacral 
foramina  decrease  in  size  from  above  downward. 

The  anterior  rami  (anterior  primary  divisions)  of  the 
sacral  spinal  nerves  pass  through  the  anterior  sacral  fora- 
mina; the  posterior  rami  (posterior  primary  divisions) 
through  the  posterior  sacral  foramina. 

Arteries  enter  and  veins  emerge  from  the  anterior  sacral 
foramina.  Both  arteries  and  veins  emerge  from  the  posterior 
sacral  foramina. 


V.  CONSTITUENTS  OF  THE  INTERVERTEBRAL 

AND  MODIFIED  INTERVERTEBRAL 

FORAMINA 

Each  intervertebral  and  modified  intervertebral  foramen 
has  the  following  constituents : 

1.  Spinal  Nerve.  4.     Fat  Tissue. 

2.  Arteries.  5.     Fibrous  Tissue 

3.  Veins.  6.     Probably  Lymphatics. 

1.    SPINAL    NERVES 

In  the  intervertebral  and  modified  intervertebral  foramina 
the  nervous  structures  present  are  the  spinal  nerves. 

(a)   Anatomy. 

Thirty-one  pairs  of  spinal  nerves  connect  the  spinal 
cord  with  the  periphery.  Twenty-three  pairs  pass  through 
the  intervertebral  foramina ;  seven  pairs,  through  the  modi- 
fied intervertebral  foramina ;  and  the  remaining  pair,  the 
coccygeal  nerves,  emerges  from  the  inferior  aperture  of  the 
sacral  canal.  Each  nerve  is  composed  of  roots,  spinal  nerve 
proper,  and  anterior,  posterior,  and,  as  a  rule,  meningeal 
rami. 

Roots.  Each  spinal  nerve  is  attached  to  the  spinal  cord  by 
two  roots,  an  anterior  root  (motor  or  efferent)  and  a  posterior 
root  (sensory  or  afferent).  The  origin  of  the  anterior  root  is  in 

43 


44  THI-:  INTERVERTEBRAL  FORAMINA  IN  MAN 

the  gray  matter  of  the  spinal  cord ;  its  emergence  is  by  several 
filaments  from  the  antero-lateral  surface  (anterior  root  zone).  The 
origin  of  the  posterior  root  is  in  the  spinal  ganglion,  an  oval  en- 
largement which  is  part  of  the  root;  its  entrance  into  the  spinal 
cord  is  by  several  filaments  through  the  postero-lateral  sulcus. 

Spinal  Nerve  Proper.  The  anterior  and  posterior  roots  of 
each  spinal  nerve  unite  to  form  the  spinal  nerve  proper.  This 
union  takes  place  either  in  the  intervertebral  foramen  or  immediately 
lateral  to  it. 

Kami.  After  passing  a  variable  distance  each  spinal  nerve 
bifurcates,  lateral  to  the  intervertebral  foramen,  into  an  anterior  and 
posterior  minus  (anterior  and  posterior  primary  division),  giving 
off,  just  before  its  bifurcation,  a  very  small  mcningeal  ramus 
(recurrent  branch).  In  connection  with  the  anterior  ramus  or  spinal 
nerve  proper,  a  sympathetic  branch  is  found  called  the  ramus 
communicans. 

(b)  Relative  Size. 

The  size  of  the  spinal  nerves  varies  greatly.  The  smallest 
nerves  are  connected  with  the  two  extremities  of  the  spinal 
cord  and  with  the  mid-thoracic  region.  The  coccygeal  nerve 
is  the  smallest  and  the  next  in  order  of  size  are  the  lower 
sacral  and  the  upper  cervical.  The  largest  nerves  are  con- 
nected with  the  cervical  and  lumbar  enlargements  of  the 
spinal  cord  and  innervate  the  upper  and  lower  limbs,  respec- 
tively; the  lower  cervical  and  first  thoracic  for  the  upper 
limbs ;  the  lower  lumbar  and  upper  sacral  for  the  lower 
limbs.  Of  these,  the  nerves  destined  for  the  lower  limbs  are 
the  larger.  The  sixth  cervical  nerves  are  the  largest  inner- 
vating the  upper  limbs ;  either  the  fifth  lumbar  or  first  sacral 
nerves  are  the  largest  innervating  the  lower  limbs,  each  of 
the  two  latter  measuring  about  7  mm.  (%5  in.)  in  diameter. 


CONSTITUENTS  OF  INTERVERTEP.RAL  FORAMINA        45 

being  the  largest  of  all  the  spinal  nerves.  The  nerves 
gradually  increase  in  the  series  passing  from  the  smaller 
toward  the  larger. 

Roots.  The  roots  correspond  in  size  with  the  spinal  nerves  of 
which  they  are  a  part.  (The  relative  size  of  the  spinal  nerves  is 
given  above.)  With  the  exception  of  the  first  cervical  nerve, 
the  posterior  root  is  always  larger  than  the  corresponding  an- 
terior one,  indicating  that  the  sensory  area  to  be  supplied  is 
greater  and  perhaps  more  abundantly  innervated  than  the  motor 
area.  The  size  of  the  spinal  ganglion  is  in  proportion  to  that  of 
the  posterior  root  of  which  it  is  a  part. 

Spinal  Nerve  Proper.  The  spinal  nerve  proper  corresponds 
in  size  with  the  spinal  nerve  of  which  it  is  a  part. 

Kami.  The  anterior  rami  (anterior  primary  divisions)  usually 
correspond  in  size  with  the  spinal  nerves  of  which  they  are  a  part. 
Therefore  the  anterior  ramus  of  the  coccygeal  is  the  smallest  and 
of  the  fifth  lumbar  or  first  sacral,  the  largest.  With  the  exception 
of  the  first  and  second  cervical  nerves,  the  anterior  rami  are  con- 
siderably larger  than  the  corresponding  posterior  rami. 

With  one  or  two  exceptions  the  posterior  rami  (posterior  primary 
divisions)  are  all  very  small.  The  posterior  ramus  of  the  second 
cervical  is  the  largest,  following  which  the  rami  in  the  cervical 
region  decrease  from  above  downward.  The  posterior  rami  of 
the  thoracic  nerves  usually  vary  but  slightly  in  size,  while  those 
of  both  the  lumbar  and  sacral  regions  decrease  from  above  down- 
ward. The  smallest  posterior  ramus  is  that  of  the  coccygeal  nerve. 

The  meningeal  rami  (recurrent  branch)  and  the  rami  com- 
municantes  are  all  very  small. 

(c)  Location  and  Divisions  in  the  Intervertebral 
Foramina. 

The  spinal  nerves  in  the  intervertebral  foramina  are, 
more  or  less,  embedded  in  fat  tissue  and  are  situated  in  the 
largest  part  of  the  foramina  ;  therefore,  in  the  cervical  region 


46  THE  INTERVERTEIJRAL  FORAMINA  IN  MAN 

they  are  in  the  middle   part,  in  the  thoracic  and  lumbar 
regions,  in  the  upper  part. 

The  divisions  of  the  spinal  nerves  that  may  be  found  in 
the  intervertebral  foramina  are  the  roots,  the  spinal  ganglion 
of  the  posterior  root  being  included,  the  spinal  nerve  proper, 
and  the  meningeal  ramus  (recurrent  ramus). 

The  meningeal  ramus  is  very  small  and  often  difficult  to  find 
in  ordinary  dissections.  It  is  given  off  from  the  spinal  nerve  just 
before  it  bifurcates  into  the  anterior  and  posterior  ramus  (anterior 
and  posterior  primary  divisions).  It  joins  with  a  branch  from  the 
sympathetic,  passes  medially  and  enters  the  intervertebral  foramen 
through  which  it  reaches  the  vertebral  canal.  There  it  supplies 
the  spinal  cord  and  its  membranes,  the  blood  vessels  of  each,  the 
vertebral  ligaments  and  the  vertebrae.  At  times  the  meningeal 
ramus  is  probably  absent  altogether,  its  place  being  taken  entirely 
by  the  meningeal  fibers  passing  in  the  substance  of  the  anterior 
root. 

The  sympathetic  nerve  fibers,  which  form  the  white  rami 
communicantes,  pass  through  certain  intervertebral  and 
modified  intervertebral  foramina.  They  are  conveyed  by  all 
the  thoracic  intervertebral  foramina ;  the  first  two  or  three 
lumbar ;  and  the  second  and  third,  or  third  and  fourth,  modi- 
fied sacral  intervertebral  foramina.  There  are  probably 
some  conveyed  through  the  third,  fourth  and  fifth  cervical 
intervertebral  foramina.*  Sympathetic  nerve  fibers,  which 
are  derived  from  the  gray  rami  communicantes,  pass  through 
all  the  intervertebral  and  modified  intervertebral  foramina. 
All  the  sympathetic  fibers  are  situated  in  the  substance  of  the 
spinal  nerves  in  their  passage  through  the  foramina. 


*These  fibers  accompany  the  phrenic  nerve. 


CONSTITUENTS  OF  INTERVERTEBRAL  FORAMINA      47 

2.    ARTERIES 

Arteries  enter  the  intervertebral  and  modified  interver- 
tebral  foramina.  As  a  rule  one  artery  of  fair  size  passes  to 
each  foramen.  This  is  known  as  the  spinal  artery.  However 
in  the  foramina,  several  arteries  of  different  sizes  are  usu- 
ally seen.  These  are,  in  all  probability,  branches  from  the 
spinal  artery.  The  disposition  of  all  the  spinal  arteries  is 
practically  the  same.  Their  function  is  to  supply  the  con- 
tents and  wall  of  the  vertebral  canal.  (The  only  other  source 
of  arterial  blood  to  the  vertebral  canal  is  from  the  anterior 
and  posterior  spinal  branches  of  the  vertebral  artery.)  The 
spinal  arteries  are  arranged  similarly  on  both  sides  of  the 
vertebral  column  and  are  derived  from  the  vertebral,  as- 
cending cervical,  and  deep  cervical  arteries  in  the  cervical 
region ;  from  the  superior  intercostal,  intercostal,  and  sub- 
costal arteries  in  the  thoracic  region ;  from  the  lumbar  and 
ilio-hnnbar  arteries  in  the  lumbar  region ;  and  from  the 
superior  and  inferior  lateral  sacral  and  middle  sacral  arteries 
in  the  sacral  region. 

The  spinal  arteries  in  the  several  regions  are  derived  as 
follows : 

Cervical  Region. 

1.  Vertebral,  branch  of  subclavian. 

2.  Ascending  cervical,  branch  of  inferior  thyroid. 

3.  Deep  cervical,  branch  of  costo-cervical  trunk    (superior  in- 

tercostal). 

The  vertebral  artery,  itself,  enters  the  modified  intervertebral 
foramen  situated  between  the  occipital  bone  and  the  atlas.  Five 
or  six  spinal  branches  are  given  off  from  the  vertebral  artery, 


48  THE  INTERVERTEBRAL  FORAMINA  IN  MAN 

the  first  one  entering  the  modified  intervertehral  foramen  between 
the  atlas  and  epistropheus  (axis)  and  the  remaining  entering  the 
first  four  or  five  intervertebral  foramina  below;  one  or  two  are 
given  off  by  the  ascending  cervical  which  enter  the  middle  cervical 
intervertebral  foramina ;  and  one  is  given  off  by  the  deep  cervical 
which  enters  the  last  cervical  intervertebral  foramen. 

Thoracic  Region. 

1.  Superior   intercostal,   branch   of  costo-cervical   trunk. 

2.  Posterior  division  of  the  intercostals,  branches  of  thoracic 

aorta. 

3.  Posterior  branch   of  subcostal,  branch  of  thoracic  aorta. 
From  the   superior  intercostal  artery  two   spinal  branches   are 

given  off  which  enter  the  first  and  second  thoracic  intervertebral 
foramen,  respectively;  from  the  posterior  divisions  of  the  nine 
intercostal  arteries,  spinal  branches  are  given  off  which  enter  the 
irtervertebral  foramina,  from  the  third  to  the  eleventh,  inclusive : 
and  from  the  posterior  branch  of  the  subcostal  artery  one  spinal 
branch  is  given  off  which  enters  the  last  thoracic  intervertebral 
foramen. 

Lumbar  Region. 

1.  Posterior    branch   of    the    lumbars,    branches   of    abdominal 

aorta. 

2.  Lumbar  division  of  the  ilio-lumbar,  branch   of  hypogastric 

(internal  iliac). 

From  the  posterior  branches  of  the  four  lumbar  arteries  spinal 
branches  are  given  off  which  enter  the  first  four  lumbar  inter- 
vertebral foramina,  and  from  the  lumbar  division  of  the  ilio-lumbar 
one  spinal  branch  is  given  off  which  enters  the  last  lumbar  in- 
tervertebral foramen. 

Sacral  Region. 

1.  Superior   lateral   sacral  )  Branches   of  hypogastric 

2.  Inferior    lateral    sacral  J       (internal  iliac). 

3.  Lateral    sacral    branches  of    the   middle    sacral,   branch    of 

abdominal  aorta. 


CONSTITUENTS  OF  INTERVERTEBRAL  FORAMINA       49 

The  superior  lateral  sacral  artery,  itself,  enters  the  first  an- 
terior sacral  foramen.  From  the  inferior  lateral  sacral  artery 
three  spinal  branches  are  given  off  which  enter  the  second,  third 
and  fourth  anterior  sacral  foramen,  respectively ;  and  from  the 
lateral  sacral  branches  of  the  middle  sacral  four  spinal  branches 
are  given  off  which  enter  the  first  four  anterior  sacral  foramina, 
respectively.  All  the  arteries  in  this  region  enter  the  anterior 
sacral  foramina  and,  after  supplying  branches  to  the  sacral  canal 
and  its  contents,  emerge  by  the  corresponding  posterior  sacral 
foramina. 

All  of  the  arteries,  with  one  exception,  which  give  off  branches 
that  enter  the  intervertebral  or  modified  intervertebral  foramina 
are  paired ;  e.  g.,  there  are  two  vertebral  arteries,  one  on  each 
side ;  two  deep  cervical  arteries,  one  on  each  side,  etc.  The  excep- 
tion is  the  middle  sacral  artery  which  is  single. 

Two  pairs  of  modified  intervertebral  foramina  have  named 
arteries  entering  them,  the  foramina  between  the  occipital  bone 
and  atlas,  which  serve  to  transmit  the  vertebral  arteries  and  the 
first  anterior  sacral  foramina  which  serve  to  transmit  the  superior 
lateral  sacral  arteries.  These  two  arteries  are  of  good  size,  the 
vertebral  being  much  the  larger. 


3.    VEINS 

Veins  emerge  from  the  intervertebral  and  modified  in- 
tervertebral foramina.  Usually  one  or  more  are  present  in 
each  foramen,  and  are  known  as  the  intervertebral  veins. 
They  convey  blood  from  the  internal  vertebral  venous  plex- 
uses, and  after  emerging  from  the  foramina,  receive  numer- 
ous branches  from  the  external  vertebral  venous  plexuses  and 
open  into  the  vertebral  vein  and  venous  plexus  in  the  cervi- 
cal region ;  into  the  intercostal  and  subcostal  in  the  thoracic 
region  ;  into  the  lumbar  and  ilio-lumbar  in  the  lumbar  region  ; 
into  the  anterior  sacral  venous  plexus  in  the  sacral  region. 


50  THE  INTERVERTEBRAL  FORAMINA  IN  MAN 

The  arrangement  is  similar  on  both  sides  of  the  vertebral 
column. 

Internal  Vertebral  Venous  Plexuses. 

The  internal  vertebral  venous  plexuses  are  located  in  the  verte- 
bral canal.  They  receive  the  venous  blood  from  the  contents 
and  wall  of  the  vertebral  canal.  Most  of  this  blood  is  drained  by 
the  intervcrtebral  veins,  although  some  is  conveyed  above  by  the 
cranial  venous  sinuses  and  also  through  the  ligamenta  flava  (liga- 
menta  subflava)  to  the  posterior  external  vertebral  venous  plexus. 

Vertebral  Vein  and  Venous  Plexus,  Intercostal,  Subcostal, 

Lumbar   and    Ilio-Lumbar   Veins   and   the 

Anterior  Sacral  Venous  Plexus. 

These  veins  and  venous  plexuses  are  situated  in  the  immediate 
vicinity  of  the  vertebral  column  in  their  respective  regions.  They 
receive  the  intervertebral  veins  and  terminate  as  follows : 

Cervical  Region.  The  vertebral  plexus  of  veins  is  situated  in 
the  upper  part  of  the  neck  terminating  as  it  descends  in  a  single 
vein,  the  vertebral  vein,  which  empties  into  the  subclavian. 

Thoracic  Region.  The  first  eleven  are  the  intercostal  veins. 
The  remaining  one  is  the  subcostal.  On  the  right  side  the  first 
intercostal  terminates  in  the  right  vertebral  or  innominate;  the 
second,  third  and  fourth  in  the  right  superior  intercostal;  the  fifth 
to  the  eleventh,  inclusive,  with  the  subcostal,  in  the  azygos  (vena 
azygos  major).  On  the  left  side  the  first  intercostal  terminates  in 
the  left  vertebral  or  innominate;  the  second,  third  and  fourth  (some- 
times), in  the  left  superior  intercostal;  the  fourth  (sometimes), 
fifth,  sixth,  seventh  and  eighth  in  the  afccssory  hemiasygos  (vena 
azygos  minor  superior)  ;  the  ninth,  tenth,  eleventh  and  subcostal  in 
the  hemiasygos  (vena  azygos  minor  inferior). 

Lumbar  Region.  The  first  four  are  the  lumbar  veins  which 
terminate  in  the  inferior  vena  cava.  The  remaining  one  is  the  ilio- 
lumbar  vein  which  terminates  in  the  common  iliat. 


CONSTITUENTS  OF  INTERVERTEBRAL  FORAMINA        51 

Sacral  Region.  The  sacral  intervertebral  veins  emerge  from 
the  anterior  sacral  foramina,  none  passing  from  the  posterior  fora- 
mina. The  anterior  sacral  venous  plexus,  previously  mentioned, 
is  formed  by  the  superior  and  inferior  lateral  sacral  and  the 
middle  sacral  veins.  The  first  sacral  intervertebral  vein  is  drained 
by  the  superior  lateral  and  the  middle  sacral  veins;  the  second, 
third  and  fourth  veins  by  the  inferior  lateral  and  the  middle  sacral 
veins.  The  superior  and  inferior  lateral  sacral  veins  terminate  in 
the  hypogastric  (internal  iliac),  and  the  middle  sacral  in  the  left 
common  iliac. 

The  arrangement  of  the  veins  corresponds  in  general  with  that 
of  the  arteries.  All  are  paired  except  the  middle  sacral  which, 
like  its  corresponding  artery,  is  single. 


4.    FAT    TISSUE 

Considerable  fat  tissue  is  found  in  the  intervertebral  and 
modified  intervertebral  foramina  and  the  immediate  sur- 
rounding parts.  It  forms  the  most  abundant  constituent  of 
the  epidural  cavity  of  the  vertebral  canal  and  the  interverte- 
bral foramina.  As  the  nervous  structures,  which  are  more 
or  less  embedded  in  the  fat  tissue,  pass  from  the  spinal  cord, 
the  fat  tissue  in  their  immediate  vicinity  gradually  decreases 
in  amount. 

It  is  well  to  remember  that  a  small  amount  of  fibrous  tissue 
is  a  normal  constituent  of  all  fat.  Fat  cells  are  developed  directly 
from  embyronic  connective  tissue  cells.  The  embryonic  connec- 
tive tissue  cells  of  developing  fat  which  are  not  destined  to  become 
fat  cells,  develop  into  cells  and  fibers  of  ordinary  fibrous  tissue 
(intralobular  connective  tissue).  A  few  of  these  cells  and  fibers 
remain  among  the  fat  cells  and  are  seen  as  such  in  adult  fat,  but 
the  majority  unite  to  form  septa  of  fibrous  tissue  (interlobular 
connective  tissue)  which  arrange  the  fat  into  groups  or  lobules. 


52  THE  INTERVERTEBRAL  FORAMINA  IN  MAN 

While  it  is  true  that  fat  tissue  practically  always  has  some  fibrous 
tissue  in  connection  with  it,  the  reverse  of  this  is  not  true. 

5.    FIBROUS    TISSUE 

There  is  very  little  fibrous  tissue  present  in  the  epidural 
cavity  of  the  vertebral  canal  and  the  intervertebral  and  modi- 
fied intervertebral  foramina,  but  laterally  it  is  much  more 
abundant.  Most  of  the  fibrous  tissue  present  is  in  associa- 
tion with  fat  tissue.  As  the  nervous  structures  pass  from 
the  spinal  cord  the  fibrous  tissue  in  their  immediate  vicinity 
gradually  increases  in  amount.  The  entire  vertebral  column 
is  practically  surrounded  by  fibrous  and  muscular  tissue. 

The  fibrous  tissue  present  in  the  vicinity  of  the  intervertebral 
foramina  is  very  abundant  and  consists  of  the  vertebral  ligaments, 
including  the  intervertebral  fibro-cartilages,  the  periosteum  of  the 
vertebrae  and  ribs,  epineurium  of  the  nervous  structures,  epimysium 
of  surrounding  muscles,  capsules  of  lymph  nodes,  walls  of  blood  and 
lymph  vessels,  the  surrounding  fasciae  and  membranes,  and  connects 
the  dura  mater  to  the  posterior  longitudinal  ligament  (posterior 
common  ligament). 

6.    LYMPHATICS 

Little  is  known  concerning  the  lymphatics  present  in  the 
intervertebral  and  modified  intervertebral  foramina.  In  the 
ordinary  stained  histologic  section  no  lymph  vessels  can  be 
recognized.  Their  presence  or  absence  can  only  be  proved 
by  special  injection  methods.  No  lymph  vessels  are  present 
in  the  spinal  cord.  However,  like  nearly  all  parts  of  the 
body,  it  has  a  lymph  supply,  the  nerve  cells  being  more  or 
less  bathed  by  lymph  contained  in  pericellular  lymph  spaces. 


CONSTITUENTS  OF  INTERVERTEBRAL  FORAMINA        53 

Perivascular  lymph  spaces  or  channels  convey  lymph  from 
the  spinal  cord.  In  all  probability  the  lymph  passes  through 
the  intervertebral  foramina  in  these  spaces  and  definite 
lymph  vessels  and  glands  are  not  formed  until  lateral  to 
them.* 


*The  only  lymphatic  structures  that  can  be  recognized  as  such  in  the  plates 
in  this  text  are  sections  through  lymph  nodes  lateral  to  the  intervertebral 
foramen.  (Plates  8,  9,  10.) 


VI.    SIZES   OF   THE   INTERVERTEBRAL    FORA- 
MINA AS  COMPARED  TO  THE  SPINAL 
NERVES 

The  intervertebral  foramina  in  each  region  increase  in 
size  from  above  downward  but  the  spinal  nerves  which  they 
transmit  do  not  increase  in  the  same  manner  and  therefore 
will  not  be  proportionate.  For  example :  The  middle  thor- 
acic intervertebral  foramina  are  larger  than  the  lower  cer- 
vical foramina,  yet  the  middle  thoracic  spinal  nerves  are 
much  smaller  than  the  lower  cervical  nerves.  (Plate  4.) 
The  greatest  proportion,  the  author  has  observed,  was  where 
about  one-third  of  the  total  area  of  the  intervertebral  fora- 
men was  occupied  by  the  spinal  nerves ;  the  smallest,  by 
about  one-twelfth.  The  intervertebral  foramina  are  largest 
in  proportion  to  the  nervous  structures,  in  the  middle  and 
lower  thoracic  regions  and  smallest  in  the  lower  cervical 
region.  Although  the  thoracic  region,  as  a  w.hole,  has  the 
least  movement  of  the  movable  regions  of  the  vertebral 
column,  the  nerves  here  appear  best  protected.  Almost  the 
reverse  is  true  of  the  cervical  region.  However  in  each  re- 
gion of  the  vertebral  column  there  is  ample  room  for  the 
passage  of  all  the  structures  through  these  apertures.  The 
sizes  of  the  intervertebral  foramina  as  compared  to  the 
spinal  nerves  is  also  dependent  to  a  considerable  extent  upon 
the  part  of  the  spinal  nerves  present  in  the  foramina.  If 
the  anterior  root  and  the  spinal  ganglion  of  the  posterior 

54 


NERVES  COMPARED  TO  INTERVERTEBRAL  FORAMINA    55 

root  are  present  in  the  intervertebral  foramen,  they  will  oc- 
cupy a  greater  area  than  when  the  spinal  nerve  proper  is 
present.  It  appears  that  the  intervertebral  foramina  are 
larger  in  proportion  to  the  spinal  nerves  they  convey,  in  the 
normal  adult  than  in  the  child,  although  it  has  not  been 
definitely  proven.  The  reason  for  this  belief  is  as  follows : 
At  birth  the  spinal  cord  extends  in  the  vertebral  canal  to  as 
low  as  the  level  of  the  body  of  the  third  lumbar  vertebra ; 
in  the  adult  it  extends  only  to  the  level  of  the  body  of  the 
first  lumbar.  This  means  that  the  vertebrae,  which  in  all 
probability  includes  the  intervertebral  foramina,  grow  more 
rapidly  than  does  the  cord.  If  the  spinal  nerves  grow  in 
proportion  to  the  growth  of  the  cord,  which  is  very  plausi- 
ble, it  appears  evident  that  the  intervertebral  foramina  grow 
faster  than  the  nerves. 


PART   II 


DETAILED  DESCRIPTION  OF  AN  INTERVERTE- 
BRAL  FORAMEN  AND  ITS  ADJACENT  PARTS 


INTRODUCTION 

The  necessary  specimen  was  secured  from  a  five-month- 
old  male  infant.  At  this  age  the  intervertebral  foramina  are 
of  such  size  as  to  be  very  suitable  for  microscopic  examina- 
tion. The  infant  had  been  normal  in  every  respect  until 
eight  days  prior  to  its  death.  At  this  time  it  developed  a 
broncho-pneumonia. 

The  right  seventh  thoracic  intervertebral  foramen  was 
selected  for  study.  The  right  half  of  the  seventh  and  eighth 
thoracic  vertebrae,  with  the  head  and  neck  of  the  right 
seventh  and  eighth  ribs  attached,  was  used  as  a  specimen. 
The  specimen  was  put  through  the  usual  histologic  tech- 
nique, the  bones  being  decalcified  with  dilute  nitric  acid. 
It  was  placed  and  mounted  on  a  block,  the  longitudinal  cut 
surface  of  the  spinal  cord  and  the  bodies  and  laminae  of 
the  vertebrae,  resting  on  the  block.  The  specimen  was  then 
cut  into  sections,  approximately  in  the  sagittal  plane,  forty- 
nine  sections  in  all  being  preserved,  there  being  an  average 
of  about  180  microns  (Vuo  in.)  between  each.  They  were 
cut  from  without  inward,  and  labeled  accordingly.  These 
sections  cut  the  spinal  nerve  almost  transversely  as  it 
emerged  from  the  intervertebral  foramen.  Section  1  shows 
structures  considerably  lateral  to  the  intervertebral  fora- 
men, while  Section  49,  the  last  one,  is  in  the  vertebral  canal. 
Photomicrographs  of  only  four  of  these  sections  (Sections 
38,  30,  27,  23)  are  given  in  this  description. 

59 


60  THE  INTERVERTEBRAL  FORAMINA  IN  MAN 

General  Description  of  Plates.  Plates  5  and  6  are  draw- 
ings which  are  shown  that  the  reader  may  better  under- 
stand the  photomicrographs  which  follow. 

Plates  7,  8,  9,  and  10  are  retouched  photomicrographs  of 
the  right  seventh  thoracic  intervertebral  foramen  and  the 
area  lateral  to  it.  Each  is  enlarged  about  10  diameters.  In 
the  retouching  no  attempt  was  made  to  conceal  the  results 
of  faulty  technique,  thus  every  part  is  shown  to  be  prac- 
tically identical  with  the  original  slides.  Each  plate  cor- 
responds to  a  section  and  is  numbered  in  the  reverse  order 
(within  outward)  from  which  the  section  was  cut.  Plate 
7,  the  first  photomicrograph,  is  Section  38  which  cuts 
through  the  intervertebral  foramen ;  and  the  remaining 
plates,  8,  9,  and  10,  are  Sections  30,  27,  and  23  respectively, 
which  are  lateral  to  the  intervertebral  foramen. 

The  photomicrographs  in  this  text  show  the  following 
nervous  structures: 

1.  Anterior  and  posterior  roots ;  spinal  ganglion  on  pos- 
terior root; 

2.  Spinal  nerve  proper  ; 

3.  Anterior  and  posterior  rami  (anterior  and  posterior 
primary  divisions)  ; 

4.  White  and  gray  rami  commnnicantes  of  the  sympa- 
thetic ; 

5.  Ganglion  of  the  sympathetic  gangliated  trunk. 


DESCRIPTION    OF    PLATE    5 

This  plate  shows  the  right  lateral  view  of  the  seventh 
thoracic  intervertebral  foramen,  together  with  the  seventh 
and  eighth  thoracic  vertebrae,  with  the  intervertebral  fibro- 
cartilage  connecting  them,  and  the  head  and  neck  of  the 
right  eighth  rib. 

Bony  Boundaries  of  Intervertebral  Foramen. 
f  Body  of  seventh  thoracic.. 
Head  of  eighth  rib. 

(The  external  lateral  part  of  the  seventh 
Anterior     \       thoracic  intervertebral  fibro-cartilage  also 
forms  an  anterior  boundary,  but  this  is 
not  shown  here,  it  being  medial  to  the 
head  of  the  rib.) 

p         .        (  Inferior  articular  process  of  seventh  thoracic. 
1  Superior  articular  process  of  eighth  thoracic. 

Superior      j  Root  (pedicle)  of  seventh  thoracic. 
Inferior       j  Root  (pedicle)  of  eighth  thoracic. 


62 


PLATE  5 


63 


A  right  lateral  view  of  the  seventh  and  eighth  thoracic  verte- 
brae with  the  intervertebral  fibro-cartilage  connecting  them,  and 
the  head  and  neck  of  the  right  eighth  rib.  Life  size. 


A — Inferior      articular      process      of 

seventh  thoracic. 
B — Root        (pedicle)        of       seventh 

thoracic. 

C — Body  of  seventh  thoracic. 
D — Intervertebral    fibro-cartilage. 


E — Head  of  eighth   rib. 

F — Root        (pedicle)        of        eighth 

thoracic. 
G — Superior     articular     process     of 

eighth   thoracic. 


DESCRIPTION    OF    PLATE    6 

This  plate  is  an  outline  drawing  of  the  right  seventh 
thoracic  intervertebral  foramen  and  its  adjacent  bony 
boundaries,  with  the  size  and  position  of  the  roots  of  the 
right  seventh  thoracic  spinal  nerve.  It  is  shown  in  detail 
in  Plate  7.  The  intervertebral  foramen  has  the  same  bony 
boundaries,  and  is  in  the  same  position  as  in  Plate  5.  Owing 
to  the  projection  of  the  bony  boundaries  at  different  levels 
the  entire  boundary  is  not  always  present  in  each  section. 
In  this  instance  it  is  deficient  inferiorly.  The  darkened  areas 
represent  the  hyaline  articular  cartilage. 

Articular  Cartilage  on  Bony  Boundaries. 

Hyaline  articular  cartilage  is  found  on  the  following 
parts : 

1.  Inferior  articular  process  of  seventh  thoracic. 

2.  Superior  articular  process  of  eighth  thoracic. 

3.  Body  of  seventh  thoracic. 

4.  Head  of  eighth  rib. 

This  articular  cartilage  is  found  on  the  articular  processes, 
and  on  the  body  of  the  vertebra  and  head  of  rib,  where  they 
articulate. 

The  size  and  position  of  the  roots  of  the  seventh  thoracic 
spinal  nerve  are  shown  in  the  upper  central  part  of  the  in- 
tervertebral foramen.  The  small  anterior  one  is  the  anterior 

66 


PLATE  6 


Root (Pedicle)  of 
Seventh  Thoracic 


Interior 

Articular 

Process 


Root (Pedicle)  of 

Eighth  Thoracic 


A  right  lateral  view  of  the  right  seventh  thoracic  intervertebral  foramen  and  its 
adjacent  bony  boundaries  with  the  position  and  size  of  the  roots  of  the  right  seventh 
thoracic  spinal  nerve.  Outline  drawing  from  Plate  7. 


DESCRIPTION  OF  PLATE  G  00 

root,  the  large  posterior  one  is  the  spinal  ganglion  of  the 
posterior  root.  The  roots  are  surrounded  by  epineurium. 
They  occupy  about  one-fifth  of  the  total  area  of  the  interver- 
tebral  foramen  and  are  free  from  any  bony  contact.  The 
other  structures  in  the  foramen,  fat  cells,  fibrous  tissue,  and 
blood  vessels,  are  shown  in  the  photomicrographs  which 
follow. 


DESCRIPTION    OF    PLATE    7     (Section  38) 

This  plate  is  the  most  medial  one  shown  in  this  series 
and  presents  a  right  lateral  view  of  the  right  seventh  thoracic 
intervertebral  foramen  and  its  adjacent  bony  boundaries.  It 
is  in  the  same  position  as  Plates  5  and  6. 

Bony  Boundaries  of  Intervertebral  Foramen. 

The  bony  boundaries  are  similar  to  those  shown  in 
Plates  5  and  6.  The  reason  for  the  deficiency  of  the  bony 
boundary  inferiorly  was  given  in  connection  with  Plate  6. 

Articular  Cartilage  of  Bony  Boundary. 

The  articular  cartilages  are  similar  to  those  shown  in 
Plate  6. 

Contents  of  Intervertebral  Foramen. 

1.  Nervous  Structures.           4.     Fibrous  Tissue 

2.  Blood  Vessels.  5.     Vacant  Spaces 

3.  Fat  Tissue. 

Lymphatics  are  undoubtedly  present  in  this  intervertebral 
foramen  but  cannot  be  recognized  in  this  photomicrograph. 
(See  paragraph  on  "Lymphatics,"  Page  52.) 

1.     Nervous  Structures. 

Anterior  root  and  the  spinal  ganglion  of  the  posterior 
root  of  spinal  nerve. 

70 


PLATE  7  (Section  38) 


-Root(  Pedicle) 
* Seventh  Thoracic 


A   right   lateral   view   of  the    right   seventh   thoracic   intervectebral    foramen   and 
its  adjacent  bony  boundaries. 


A — Vacant   space. 

B — Capsular    ligament. 

C — Fat  tissue. 

D — Articular   cartilages. 

E — Fibrous  tissue. 


F — Kpinenrium. 

G — Anterior   root  of  spinal  nerve. 
II — Spinal   ganglion   of  posterior  root  of  spinal 
nerve. 

I — Blood  vessel. 

J — Articular    cartilages. 


DESCRIPTION  OF  PLATE  7  73 

The  position  of  the  roots  has  been  discussed  in  con- 
nection with  Plate  (5.  The  epineurium  surrounds  each  root 
separately  and  also  serves  to  bind  them  together  as  a  whole. 
They  are  free  from  any  bony  contact  and  are  embedded  in 
fat  tissue. 

2.  Blood  Vessels. 

Numerous  blood  vessels  of  various  sizes  are  embedded 
in  the  fat  tissue. 

3.  Fat  Tissue. 

Fat  forms  the  most  abundant  constituent  of  the  foramen. 

4.  Fibrous  Tissue. 

Fibrous  tissue  forms  the  epineurium  of  the  nervous 
structures,  the  periosteum  of  the  bones,  and  part  of  the  walls 
of  the  blood  vessels,  and  is  a  constituent  of  the  fat  tissue. 
This  is  true  in  all  the  sections.  It  is  well  to  remember  that 
all  fat  tissue  has  more  or  less  fibrous  tissue  in  connection 
with  it.  The  capsular  ligament  connecting  the  articular 
processes,  is  composed  of  fibrous  tissue. 

5.  Vacant  Spaces. 

Spaces  occur  in  which  all  tissue  is  absent.  In  the  photo- 
micrographs these  vacant  spaces  are  difficult  to  distinguish 
from  blood  vessels.  However  in  the  case  of  the  blood  ves- 
sels the  walls  are  thick,  while  in  the  vacant  spaces  this  is 
not  true.  The  vacant  spaces  are,  no  doubt,  due  to  faulty 
technique  and  'probably  represent  areas  where  fat  cells  have 
been  washed  out  in  the  process  of  preparing  the  specimen. 
The  above  is  true  in  all  the  sections. 


DESCRIPTION    OF    PLATE    8     (Section  30) 

This  is  immediately  lateral  to  the  right  seventh  thoracic 
intervertebral  foramen. 

Bony  Relations  Lateral  to  Intervertebral  Foramen. 

Anterior  {  Head  of  seventh  rib" 
(  Head  of  eighth  rib. 

p         .      J  Inferior  articular  process  of  seventh  thoracic. 
(  Superior  articular  process  of  eighth  thoracic. 

Superior   j  Root  (pedicle)  of  seventh  thoracic. 

In  this  and  in  the  following  photomicrographs  the  posi- 
tions of  the  bony  parts  are  named  according  to  their  rela- 
tions to  the  cerebro-spinal  nervous  structures. 

The  heads  of  the  seventh  and  eighth  ribs  are  shown  in- 
stead of  the  body  of  the  seventh  thoracic,  and  the  root 
(pedicle)  of  the  eighth  thoracic  has  disappeared. 

Articular  Cartilages. 

Articular  cartilage  is  found  on  the  following  parts : 

1.  Inferior  articular  process  of  seventh  thoracic. 

2.  Superior  articular  process  of  eighth  thoracic. 

Tissues  Lateral  to  Intervertebral  Foramen. 

The  tissues  present  are  the  same  as  those  shown  in  the 
former  plate  except  for  the  addition  of  lymphoid  tissue. 

74 


PLATE  8  (Section  30) 


Root (Pedicle)   of 
Seventh  Thorac ic 


. 
Superior 

Articularj 
Process 


A  right  lateral  view  immediately  lateral  to  the  right  seventh  thoracic  intervertebral 
foramen. 


A — Spinal   nerve. 

B — Capsular   ligament. 

C — Vacant   space. 

D — Articular   cartilages. 


E — Fibrous  tissue. 
F — Blood    vessel. 
G — Fat  cells. 
H — Lymph  node. 


DESCRIPTION  OF  PLATE  8  77 

1.  Nervous  Structures. 

The  spinal  nerve  proper. 

The  anterior  and  posterior  roots  seen  in  the  former 
plate  have  united  and  the  spinal  nerve  proper  is  formed.  It 
is  surrounded  by  epineurium  and  blood  vessels,  and  is  em- 
bedded in  fat. 

2.  Blood  Vessels. 

Numerous  blood  vessels  of  various  sizes  are  embedded  in 
fat  tissue,  as  shown  in  the  former  plate. 

3.  Fat  Tissue. 

Fat  is  the  most  abundant  tissue  present. 

4.  Fibrous  Tissue. 

The  fibrous  tissue  is  arranged  as  shown  in  the  former 
plate  except  that  it  appears  slightly  increased  in  amount. 

5.  Lymphoid  Tissue. 

A  lymph  node  is  present  anterior  to  the  head  of  the 
eighth  rib. 


DESCRIPTION    OF    PLATE    9     (Section  27) 

This  is  lateral  to  the  right  seventh  thoracic  intervertebral 
foramen,  lateral  to  section  shown  in  Plate  8. 


Anterior  ) 


Bony  Relations  Lateral  to  Intervertebral  Foramen. 

Head  of  seventh  rib. 
Head  of  eighth  rib. 

Posterior  j  Inferior  articular  process  of  seventh  thoracic. 
Superior    j  Root  (pedicle)  of  seventh  thoracic. 

The  superior  articular  process  of  the  eighth  thoracic  has 
disappeared,  the  articular  cartilage  only  remaining. 

Articular  Cartilage. 

The  articular  cartilages  are  the  same  as  shown  in  the 
former  plate. 

Tissues  Lateral  to  Intervertebral  Foramen. 

The  tissues  present  are  the  same  as  those  shown  in  the 
former  plate. 

1.     Nervous  Structures. 

Anterior    and   posterior    rami    (anterior   and    posterior 
primary  divisions)  of  spinal  nerve. 

The  spinal  nerve  proper  seen  in  the  former  plate  has 

78 


PLATE  9  (Section  27) 


79 


. 

$Root( Pedicle) 

\    Seventh 


A  right  lateral  view  lateral  to  the  right  seventh  thoracic   intervertebral   foramen 
lateral  to  Plate  8. 


A — Anterior  ramus   (anterior  primary  division) 

of  spinal  nerve. 
E — Posterior  ramus  (posterior  primary  division) 

of  spinal  nerve. 
C — Capsular  ligament. 
1) — Articular  cartilages. 


I". — Blood  vessel. 
F — Fibrous  tissue. 
G — Vacant  space. 
H — Lymph  nodes. 


DESCRIPTION  OF  PLATE  9  81 

bifurcated  into  an  anterior  and  a  posterior  ramus.  As  is 
usual,  the  anterior  ramus  is  the  larger  of  the  two.  The 
rami  are  separated  by  fibrous  tissue  and  are  embedded  in  fat. 

2.  Blood  Vessels. 

The  blood  vessels  are  arranged  as  in  the  former  plates. 

3.  Fat  Tissue. 

Fat  tissue  is  the  most  abundant  tissue  present. 

4.  Fibrous  Tissue. 

The  fibrous  tissue  is  slightly  increased  in  amount. 

5.  Lymphoid  Tissue. 

Two  lymph  nodes  are  present  between  the  heads  of  the 
ribs. 


DESCRIPTION    OF    PLATE    10     (Section  23) 

This  is  lateral  to  the  right  seventh  thoracic  intervertebral 
foramen,  lateral  to  section  shown  in  Plate  9. 


Anterior     ) 


Bony  Relations  Lateral  to  Intervertebral  Foramen. 

Neck  of  seventh  rib. 
Neck  of  eighth  rib. 

Posterior    I  Transverse  process  of  seventh  thoracic. 
Superior    j  Transverse  process  of  seventh  thoracic. 

The  transverse  process  of  the  seventh  thoracic  is  shown 
instead  of  the  root  (pedicle)  and  the  inferior  articular 
process  of  this  vertebra.  The  necks  of  the  ribs  are  shown 
instead  of  the  heads. 

Articular  Cartilages. 

None  of  the  bones  present  articulate  with  one  another, 
hence  no  articular  cartilages  are  present. 

Tissues  Lateral  to  Intervertebral  Foramen. 

The  tissues  present  are  the  same  as  those  shown  in  the 
former  plate. 

1.     Nervous  Structures. 

Anterior  and  posterior  rami  (anterior  and  posterior 
primary  divisions)  of  spinal  nerve. 

82 


PLATE  10  (Section  23) 


83 


A   right   lateral   view   lateral   to   the   right   seventh    thoracic    intervertebral    foramen 
lateral  to  Plate  9.* 


A — Vacant  space. 
B — Blood  vessel. 
C — Anterior  ramus  (anterior  primary  division) 

of  spinal  nerve. 
D — Posterior     ramus     (posterior     division)     of 

spinal  nerve. 
E — Fibrous  tissue. 


F — Fat  tissue. 

G — Lymph  nodes. 

H — Sympathetic  ganglion  of  sympathetic  trunk. 


'The  label  on  each  rib  should  read  "neck"  instead  of  "head." 


DESCRIPTION  OF  PLATE  10  85 

Sympathetic  ganglion  of  the  sympathetic  trunk. 

The  rami  are  embedded  in  fatty-fibrous  tissue.  Resting 
on  the  anterior  surface  of  the  neck  of  the  eighth  rib,  a 
sympathetic  ganglion  is  present.  Like  all  nerves,  it  is  sur- 
rounded by  epineurium.  It  also  is  embedded  in  fatty-fibrous 
tissue. 

2.  Blood  Vessels. 

The  blood  vessels  are  arranged  as  in  the  former  plates, 
and  are  embedded  in  fatty-fibrous  tissue 

3.  Fat  Tissue. 

Fat  remains  the  most  abundant  tissue.  There  is  consid- 
erable fibrous  tissue  loosely  arranged,  in  connection  with  it. 

4.  Fibrous  Tissue. 

The  fibrous  tissue  is  slightly  increased  in  amount. 

5.  Lymphoid  Tissue. 

Two  lymph  nodes  are  present  between  the  necks  of  the 
ribs. 


DESCRIPTION  OF  PLATE  11  (Special) 

This  plate  is  from  the  author's  book  "The  Intervertebral 
Foramen."  It  is  shown  here  in  order  that  the  reader  may 
see  the  white  and  gray  rami  cormmmicantes  of  the  sympa- 
thetic. (The  above  nervous  structures  are  not  shown  in  the 
foregoing  photomicrographs.) 

The  plate  shows  a  right  lateral  view  lateral  to  the  right 
first  thoracic  intervertebral  foramen  of  the  cat,  and  is  en- 
larged about  13  diameters.  It  is  in  the  same  position  and 
has  the  same  relations  as  the  section  shown  in  Plate  10.  This 
intervertebral  foramen  has  the  same  boundaries  as  has  the 
seventh  thoracic. 

The  nervous  structures  present  are  seen  just  beneath  the 
transverse  process  of  the  upper  vertebra.  The  large  anterior 
one  is  the  anterior  ramus  (anterior  primary  division)  of  the 
spinal  nerve.  Several  smaller  filaments  are  seen  immediately 
posterior  to  the  anterior  ramus.  These  constitute  the  pos- 
terior ramus  (posterior  primary  division)  of  the  spinal  nerve. 
Embedded  in  fibrous  tissue,  anterior  to  the  anterior  ramus, 
two  very  small  nerve  filaments,  very  closely  associated,  are 
seen.*  These  constitute  the  white  and  gray  rami  communi- 
cantes  of  the  sympathetic.  They  connect  the  anterior  ramus 
with  the  nearest  ganglion  of  the  sympathetic  gangliated 
trunk. 

All  the  nervous  structures  are  embedded  in  fibrous  tissue. 
This  tissue  is  more  dense  than  that  shown  in  the  foregoing 
plates. 

*These  findings  agree  with  those  of  T.angley  who  writes  in  Schnfer's 
Physiology:  "The  uppermost  thoracic  white  and  grey  rami  are  too  closely 
associated  to  be  cut  separately." 

86 


PLATE   11  (Special) 


A   right   lateral  view   lateral   to  the   right   first   thoracic   inter- 
vertebral    foramen. 


A — Blood  vessel. 

B — Fatty-fibrous  tissue. 

C — Posterior  ramus  (posterior  primary 

division)  of  spinal  nerve. 
D — Fibrous   tissue. 
F, — Blood  vessel. 
F — Blood  vessel. 
C — Blood  vessel. 


II — Xutrient  foramen. 

I — Anterior  ramus    (anterior  primary 

division)  of  spinal  nerve. 
J — White  and  gray  raini  coinmunicantes 

of   sympathetic. 
K — Blood   vessels. 
I. — Fat   cells. 
M — Voluntary   muscle. 


SUMMARY  OF  THIS  INTERVERTEBRAL  FORA- 
MEN AND  ITS  ADJACENT   PARTS 

Medial  to  Intervertebral  Foramen.  Immediately  me- 
dial to  the  intervertebral  foramen  the  epidural  cavity  of  the 
vertebral  canal  is  entered.  Although  no  photomicrographs 
are  shown  in  this  text  of  the  epidural  cavity  opposite  this 
intervertebral  foramen,  the  following  is  its  structure :  It  lies 
between  the  dura  mater  and  the  bony  boundaries  of  the  ver- 
tebral canal.  The  most  abundant  constituent  is  fat  tissue, 
in  fact  it  is  almost  completely  filled  with  fat.  The  roots  of 
the  spinal  nerve  and  the  blood  vessels  are  embedded  in  this 
fat.  Very  little  fibrous  tissue  is  present.* 

Intervertebral  Foramen.  The  most  abundant  constitu- 
ent of  the  intervertebral  foramen  is  fat  tissue.  The  roots 
of  the  spinal  nerve,  including  the  spinal  ganglion,  which  are 
situated  here,  are  embedded  in  fat  tissue.  They  occupy  about 
one-fifth  of  the  total  area  of  the  foramen.  The  blood  vessels, 
which  are  several  in  number  and  of  various  sizes,  are  em- 
bedded in  fat  tissue.  There  is  a  small  amount  of  fibrous 
tissue  present. 

Lateral  to  Intervertebral  Foramen.  The  most  abun- 
dant constituent  is  fat  tissue.  It  is,  however,  infiltrated  with 
a  more  or  less  loosely  arranged  fibrous  tissue,  making  a 
fatty-fibrous  tissue.  The  spinal  nerve  proper,  the  rami  (pri- 


*In    "The    Intervertebral    Foramen,"    the    author's    previous    work,    photo- 
micrographs of  the   vertebral  canal   are  shown   in  Plates   5,  6,   7,  and  8. 

89 


90  THE  LNTERVERTEBRAL  FORAMINA  ix  MAN 

mary  divisions)  of  the  spinal  nerve,  and  the  sympathetic 
ganglion  are  present.  They  are  all  more  or  less  embedded  in 
fatty-fibrous  tissue.  The  blood  vessels,  which  are  several  in 
number  and  of  various  sizes,  as  in  the  intervertebral  foramen, 
are  embedded  in  fatty-fibrous  tissue.  Several  lymph  nodes 
are  present. 


PART   III 


SUMMARY 


GENERAL  SUMMARY 

Having  spent  considerable  time,  covering  a  period  of 
over  four  years,  studying  various  intervertebral  foramina, 
with  their  contents  and  adjacent  parts,  microscopically  and 
macroscopically,  both  in  man  and  animal,  I  can  briefly 
summarize  my  findings  concerning  the  normal  morphology 
of  these  apertures  and  parts  as  follows : 

1.  All  of  the  intervertebral  foramina,  including  their 
contents  and  the  areas  immediately  medial  and  lateral  to 
them,  have  a  similar  structure. 

2.  They  are  almost  entirely  surrounded  by  bone,  the 
intervertebral  fibre-cartilages  completing  the  boundary. 

3.  In  each  region  they  have  a  characteristic  shape,  but 
all  are  more  or  less  oval,  with  the  greatest  diameter  in  a 
supero-inferior  direction.     The  greatest  antero-posterior  di- 
ameter in  the  cervical  region  is  through  the  middle ;  in  the 
thoracic  and  lumbar,  in  the  upper  part. 

4.  In  general,  they  increase  in  size  from  above  down- 
wards, being  smallest  in  the  cervical  and  largest  in  the  lum- 
bar regions. 

5.  They  are  dependent  to  a  great  extent,  as  to  size, 
upon  the  thickness  of  the  intervertebral  fibre-cartilages  and 
the  articular  cartilage  on  the  articular  processes,  especially 
the  former. 

93 


94  THE  INTERVERTEBRAL  FORAMINA  IN  MAN 

6.  They  are  subject  to  changes  in  size  and  shape,  de- 
pending upon  the  position  of  the  vertebral  column. 

7.  Each  intervertebral  foramen  has  the  following  con- 
stituents: (1)  spinal  nerve,  (2)  arteries,  (3)  veins,  (4)  fat 
tissue,   (5)   fibrous  tissue,  and  in  all  probability  (6)   lym- 
phatics. 

8.  The  sympathetic  nerve  fibres  which  pass  through  the 
intervertebral  foramina  are  in  the  substance  of  the  spinal 
nerves. 

9.  The  divisions  of  the  spinal  nerves  that  may  be  found 
in  the  intervertebral  foramina  are  the  roots,  the  spinal  gang- 
lion on  the  posterior  root  being  included,  the  spinal  nerve 
proper,  and  the  meningeal  ramus  (recurrent  ramus). 

10.  The  spinal  nerves  are  situated  in  the  largest  part  of 
the  intervertebral  foramina ;  therefore  in  the  cervical  region 
they  are  in  the  middle  part,  in  the  thoracic  and  lumbar  re- 
gions, in  the  upper  part. 

11.  The  intervertebral  foramina  are  not  proportionate  in 
size  to  the  spinal  nerves  they  convey. 

12.  They  are,  for  the  most  part,  large,  as  compared  to 
the  spinal  nerves  which  they  transmit. 

13.  The  spinal  nerves  are,  as  a  rule,  embedded  in  fat 
tissue  in  the  intervertebral  foramina. 

14.  The  most  abundant  constituent  of  the  intervertebral 
foramina  and  the  areas  immediately  medial  and  lateral  to 
them,  is  fat  tissue. 


GENERAL  SUMMARY  95 

15.  Lateral  to  the  intervertebral  foramina  there  is  con- 
siderable fibrous  tissue  present.    In  fact  the  entire  vertebral 
column  is  practically  surrounded  by  fibrous  and  muscular 
tissue. 

16.  The  fat  tissue  in  the  immediate  vicinity  of  the  spinal 
nerves  gradually  decreases  and  the  fibrous  tissue  increases  in 
passing  from  the  spinal  cord. 

17.  The  nervous  structures  are  embedded  in  fat  tissue 
in  the  vertebral  canal  and  the  intervertebral  foramina ;  in 
a  more  or  less  loosely  arranged  fibrous  or  fatty-fibrous  tissue 
lateral  to  the  intervertebral  foramina. 


Date  Due 


DEC  2 


PRINTED  IN   U.S.A.  CAT.     NO.     24      161 


UC  SOUTHERN  REGIONAL  LIBRARY  FACILITY 


A  000  421  709  7 


WET25 
S9721 

1915 
Svanberg,  Harold. 

The  intervertebral  foramina  in  man 


MEDICAL  SCIENCES  LIBRARY 

UNIVERSITY  OF  CALIFORNIA,  IRVINE 

IRVINE,  CALIFORNIA  92664 


